Apparatus for the separate discharge of flat items from a stack

ABSTRACT

Apparatus for separating and individually discharging relatively flat items from a stack includes first and second separators operatively connected by a suction conveyor belt with a plurality of groups of suction openings. In the area of the second separator an abutment member is positioned to be movable to temporarily block the conveying path before each arrival of an item from the first separator. The movement of the abutment member is effected through a pneumatic setting device that can be selectively connected with a source of subatmospheric pressure by a valve associated with the groups of suction openings in suction conveyor belt.

United States Patent H 1 Burkhardt l l May 1, 1973 [54] APPARATUS FOR THE SEPARATE [56] References Cited DISCHARGE OF FLAT ITEMS FROM A UNITED STATES PATENTS STACK 1,693,272 11/1928 Elsas et a1 ..271/74 [75] Inventor: Burkhardh Re'chenau'Mlt' 3,504,909 4 1970 Burkhardt ..271 11 telzell, Germany [73] Assignee: TELEFUNKEN Patentverwertung- Primary Examiner"'Harvey HQmSbY sgesenschaft mbH, UlmlDanilbe Assistant Examiner-James W. Miller Germany Attorney-George H. Spencer et al. [22] Filed: Dec. 15, 1971 57 ABSTRACT PP'- N05 208,312 Apparatus for separating and individually discharging relatively flat items from a stack includes first and [30] Foreign Application Priority Data second separators operatively connected by a suction conveyor belt with a plurality of groups of suction Dec. 24, 1970 Germany ..P 20 63 874.8 openings. In the area of the second separator an abut- Dec.24, 1970 Germany ..P 70 47 771.3 ment member is positioned to be movable to temporarily block the conveying path before each arrival [52] US. Cl. ..271/11, 271/26 ES, 271/74 of an item from the first separator. The movement of [51] Int. Cl ..B65h 3/12, B65h 3/46 the abutmen m mb r i eff cte through a pneum tic [58] Field of Search ..271/26 ES, 74, 34, setting device that can be selectively connected with a 271/35 source of subatmospheric pressure by a valve associated with the groups of suction openings in suction conveyor belt.

5 Claims, 2 Drawing Figures BACKGROUND OF THE INVENTION This invention relates to a device for the separate discharge of flat items, such as letters, from a stack where the output of a first separator which receives items from the stack is followed by the input of a second separator and a testing member, which is disposed in the area of the second separator, influences the separating process at the first separator in dependence on the fill state of the second separator.

In previously known devices, of the type disclosed in my U.S. Pat. No. 3,504,909, issued on Apr. 7, 1970, a first separator is provided in which one or more suction members is adapted to grip, in periodic sequence, the respective foremost or top item in the stack and convey it in a direction toward the second separator. Associated with this first separator there is an interrupter which prevents the removal of an item from the stack by a suction member when it receives a signal from the testing member associated with the second separator.

The second separator has one or more suction members which are moved in the same period and in such a time relationship with respect to the first separator that they grip the items delivered from the first separator only after they have been delayed in the area of the second separator.

At the second separator there is an interrogating device which permits a signal from the testing member, corresponding to the presence of an item in the area of the second separator, to periodically reach the interrupter only within a predetermined time interval, which lies between the release of the testing member by the trailing edge of an individual item gripped by a suction member of the second separator and the response of the testing member to the leading edge ofthe next item.

According to a further embodiment of the device disclosed in my previous patent, an abutment which serves to delay the items in the area of the second separator is moved back and forth in a direction transverse to the suction conveyor belt of this separator in synchronism with the passage of successive groups of suction openings so that it temporarily blocks the conveying path before the arrival of each item from the first separator.

The abutment, serving to delay the items in the area of the input to the second separator, may be moved back and forth, for example, mechanically by means of a cam disc which itself is driven without slip with respect to the groups of holes, or suction openings, of the suction conveyor belt. In order to assure a slipfree drive, the suction conveyor belt must either be made as a toothed belt or, when it is designed as a flat belt, it must be provided with perforations along its edge which cooperate with the corresponding protrusions of the respective roller at the cam disc. In the former case fabrication is expensive and in the latter case there is relatively rapid wear at the belt perforations.

Another embodiment utilizes a setting magnet for the drive of the abutment, the magnet being actuated by a photoelectric scanner which responds to the group of holes in the suction conveyor belt. A drawback of this arrangement, inter alia, is the limited life of the setting magnet.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an improved drive means for the above-mentioned abutment as well as an arrangement to ensure the dependable control of these means.

In general the drive means for the abutment, according to the invention, contains a pneumatic setting member whose connection with the pressure supply source is controlled by a valve which cooperates with the suction openings of the suction conveyor belt.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic plan view, partially in section, of one embodiment of a separator device according to the present invention.

FIG. 2 is an enlarged, partly broken away, sectional view of a portion of the embodiment of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the arrangement shown in FIG. 1, two suction conveyor separators are connected in tandem with a first separator having a suction trough 1 and the second separator having suction trough 2. Both suction troughs are connected to a suitable suction source (not shown). A common suction conveyor belt 3, provided for both separators, is guided over guide rollers 4 and 5 and is driven continuously. The suction conveyor belt is provided with a plurality (e.g. four). of groups of suction openings 3' which are uniformly distributed over its periphery by means of which one of the items of stack 6 is removed at a time. The leading edges of the items are aligned along a wall 7.

The suction conveyor belt 3 passes between the output of the first separator and the intake range of the second separator through a detour loop formed by rollers 8, 9 and 10 so that each group of suction openings (groups of holes) 3 arrives in the takeup range of the second separator later than the item removed from the stack and carried along by this same group of holes.

At the output of each one of the two separators, pneumatic strippers 11 or 12, respectively, of a known design, are arranged opposite the suction conveyor belt 3. Conveying rollers 13 and 14 are also provided which, in cooperation with rollers 8 and 4, respectively, forces the items to move on after they leave the effective range of the suction troughs l and 2.

In an advantageous manner a member for delaying the items is disposed in the conveying path of the second separator. This member is an abutment 15' in the illustrated embodiment against which the items from stack 6 are directed with the cooperation of a guide fence 16. This abutment is moved back and forth in a direction transverse to the suction conveyor belt 3 and in synchronism with the succession of the groups of suction openings 3' so that it temporarily blocks the conveying path before an item arrives from the first separator.

The abutment 15 can engage the suction conveyor belt 3 within the area of the suction trough 2 facing the suction conveyor belt 3. As best seen in FIG. 2 the abutment 15 is carried at the end of one of the forklike arms of a three-armed lever consisting of arms 70, 71 and 72. The lever is suitably mounted to be pivotal about an axis 73. In the illustrated position the three-armed lever is held in engagement with conveyor belt 3 by a tension spring 74 which is connected to arm 71.

The three-armed lever with abutment is driven from the illustrated closed position into a second, open position, which is limited by an abutment pin 75 cooperating with lever 71, by means of a pneumatic setting member which engages at arm 72. The setting member is a pneumatic cylinder 76 whose piston 76 is substantially supported from the end of lever arm 72 by means of shaft 72. Cylinder and piston are connected together by a roll diaphragm 76".

In the illustrated embodiment the pressure source for the pneumatic cylinder 76 is the subatmospheric pressure source to which suction troughs 1 and 2 are connected. A valve which cooperates with the suction openings 3' of the suction conveyor belt 3 serves to control the cylinder 76. This valve includes a housing 77 which is connected, via a first line 78, with the pneumatic cylinder 76 and, via a second line 79, in which a choke 79 is disposed, with the suction line 2' of suction trough 2. The housing has a wall 77', which is in contact with suction conveyor belt 3, and in which a control opening 77 is adapted to the position of the suction openings 3'. The valve arrangement can be called a control trough.

As long as the control opening 77 of the valve is closed by the suction conveyor belt 3, subatmospheric pressure is present in pneumatic cylinder 76 via housing 77 and line 78. The piston 76 is thus sucked into cylinder 76 and abutment 15 is open. During each passage of the groups of holes 3' past the control opening 77" the housing is connected with the external pressure so that the subatmospheric pressure collapses due to the presence of choke 79 and the abutment can be moved into its closed position by tension spring 74.

An interrupter of known construction is disposed at the first separator, which removes the items from stack 6, so that the removal of an item is prevented when the interrupter receives a signal. The interrupter shown here has an electromagnetically actuatable valve 46 which in its rest position (suction position) connects the suction trough 1 of this separator with the suction air source (not shown) and which in its operating position (separating position) permits normal pressure or excess pressure to be produced in the suction trough 1.

In the area of the second separator the testing member, to determine the presence of an item in this separator, is provided in the form of a light barrier composed of a generator 23 and a receiver 23 with output stage 23. The output of the light barrier is connected with valve 46 via an AND circuit 24 and a switching stage 25.

The output of an interrogation device is connected with the second input of the AND circuit 24 which permits the signal from the output stage 23 of the light barrier to reach valve 46 of suction trough 1 at periodic intervals only within a fixed period of time which lies between the release of the light barrier 23 by the trailing edge of an item leaving the second separator and the response of the light barrier to the leading edge of the next item. The interrogation device is synchronized for this purpose with the rotation of the suction openings by suitable means.

As shown in FIG. 1, the interrogation device includes a light barrier with a generator 26, a receiver 26" and an output stage 26. This light barrier responds to the passage of the individual groups of suction openings 3' and is disposed at such a point of the suction conveyor belt 3 where its output signal falls in the above-mentioned time period.

The operation of the apparatus, according to the invention, will now be described, first for the condition where no items are disposed in the areas of the two separators and the device is put into operation after a stack 6 of items has been placed thereinto. Valve 46 is in suction position. The first group of suction openings 3' of suction conveyor belt 3 which enters into the suction range of the suction trough 1 thus grips the first item of the stack in contact therewith and brings it, with the cooperation of rollers 8 and 13, along guide fence 16 into the area of the second separator. Here it is temporarily stopped at abutment 15 which now blocks the conveying path but immediately releases it again. Shortly thereafter (due to the detour via rollers 8, 9 and 10) the first group of suction openings 3 also arrives, grips the item in the suction range of suction trough 2 and brings it to the output of the second separator, formed by rollers 4 and 14 from which it leaves in the direction of the arrow 27.

During this process, a signal is emitted from output stage 23 of the light barrier as long as the barrier is interrupted by the item. This signal, however, cannot reach switching stage 25 and close valve 46 because at the second input of the AND circuit 24 there is no signal from the output stage 26 of interrogation device. The latter signal is produced only at the moment where the light barrier 23 has been released by the trailing edge of the item.

Valve 46 thus remains in the rest or open position to maintain suction in trough 1. The next group of suction openings 3 which arrives in the suction range of suction trough 1 a short time after the onset of the interrogation signal, thus removes the next item from stack 6 and the above described process is repeated.

The situation shall now be considered where, during the removal of the first item from stack 6, a further item was carried along which is assumed to adhere to the first item so tightly that in spite of the presence of pneumatic strippers 11 this further item also reached the area of the second separator. However, based on statistical principles, it is very unlikely that the two items will continue to adhere to each other duringthe second separation process that takes place at suction trough 2. Rather, only the first item will be removed by the suction openings 3 while the second item remains in the area of the second separator. Consequently, the signal from the output stage 23 of the light barrier continues and is switched through to valve 46 by the subsequent signal received from the output stage 26 interrogation device in AND circuit 24. The valve 46 thusis effective to separate the suction trough 1 from the source of subatmospheric pressure so that no item is removed from stack 6 by the next group of suction openings 3 entering into the suction range of suction trough 1.

As soon as this next group of section openings reach the area of the suction trough 2 of the second separator, they grip the item left at this point and remove it.

With the next signal from the output stage 26 of the interrogation device the light barrier 23 is free again so that valve 46, which in the meantime has returned to its suction position, remains there and the next item is removed from stack 6 at the proper time.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

I claim:

1. ln apparatus for separating and individually discharging relatively flat items from a stack, and including first and second suction separators; a suction conveyor belt having a plurality of groups of suction openings distributed along the entire length of the belt, the belt being disposed to pass adjacent the suction separators so that the items are gripped at the suction openings in the area of these separators, an abutment member in the area of the second separator which is movable transversely to the suction conveyor belt and in synchronism with the passage of successive groups of suction openings to temporarily block the conveying path before each arrival of an item from the first separator, the improvement which comprises in combination:

a. pneumatic setting means operatively associated with said abutment member and responsive to subatmospheric pressure for driving said member from a non-blocking to a blocking position relative to the conveying path;

b. a connecting line between said pneumatic setting means and a subatmospheric pressure source; and

c. a valve in said connecting line, said valve being associated with the suction conveyor belt for interrupting the application of subatmospheric pressure to said setting means during those time intervals when the successive groups of openings in the belt pass said valve, said abutment member being in a non-blocking position during the time subatmospheric pressure is maintained at said setting means and said abutment member occupying a blocking position when the subatmospheric pres sure is not maintained therein.

2. An arrangement as defined in claim 1, wherein said valve further comprises:

d. a housing connected to said pneumatic setting means by a first section of said connecting line and to the subatmospheric pressure source by a second section of said line, with said second section having a restricted opening into said housing; and

e. said housing having a wall portion which is in contact with the suction conveyor belt and which is provided with control openings disposed to cooperate with the suction openings in the belt.

3. An arrangement as defined in claim 2, wherein said second section of said line is connected to the same subatmospheric pressure source as the suction separators.

4. An arrangement as defined in claim 2, wherein said pneumatic setting means further comprises:

f. a cylinder with a piston therein and connected to said first section of said connecting line; and

g. lever means disposed between said piston and the abutment member, said lever means being pivotally mounted and resiliently urged in a direction which urges said abutment member into its blocking position.

5. An arrangement as defined in claim 4, wherein said lever means is three-armed, one of the arms being connected to said piston, another arm being connected to the abutment member, and the third arm being connected to means resiliently urging the abutment member in such direction. 

1. In apparatus for separating and individually discharging relatively flat items from a stack, and including first and second suction separators; a suction conveyor belt having a plurality of groups of suction openings distributed along the entire length of the belt, the belt being disposed to pass adjacent the suction separators so that the items are gripped at the suction openings in the area of these separators, an abutment member in the area of the second separator which is movable transversely to the suction conveyor belt and in synchronism with the passage of successive groups of suction openings to temporarily block the conveying path before each arrival of an item from the first separator, the improvement which comprises in combination: a. pneumatic setting means operatively associated with said abutment member and responsive to subatmospheric pressure for driving said member from a non-blocking to a blocking position relative to thE conveying path; b. a connecting line between said pneumatic setting means and a subatmospheric pressure source; and c. a valve in said connecting line, said valve being associated with the suction conveyor belt for interrupting the application of subatmospheric pressure to said setting means during those time intervals when the successive groups of openings in the belt pass said valve, said abutment member being in a nonblocking position during the time subatmospheric pressure is maintained at said setting means and said abutment member occupying a blocking position when the subatmospheric pressure is not maintained therein.
 2. An arrangement as defined in claim 1, wherein said valve further comprises: d. a housing connected to said pneumatic setting means by a first section of said connecting line and to the subatmospheric pressure source by a second section of said line, with said second section having a restricted opening into said housing; and e. said housing having a wall portion which is in contact with the suction conveyor belt and which is provided with control openings disposed to cooperate with the suction openings in the belt.
 3. An arrangement as defined in claim 2, wherein said second section of said line is connected to the same subatmospheric pressure source as the suction separators.
 4. An arrangement as defined in claim 2, wherein said pneumatic setting means further comprises: f. a cylinder with a piston therein and connected to said first section of said connecting line; and g. lever means disposed between said piston and the abutment member, said lever means being pivotally mounted and resiliently urged in a direction which urges said abutment member into its blocking position.
 5. An arrangement as defined in claim 4, wherein said lever means is three-armed, one of the arms being connected to said piston, another arm being connected to the abutment member, and the third arm being connected to means resiliently urging the abutment member in such direction. 